I THE NEW HEAVENS 

I GEORGE ELLERY HALE 

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THE NEW HEAVENS 




Fig. I. The Constellation of Orion (Hubble). 

Photographed with a small camera lens of i inch aperture and 5 inches focal 
length. The three bright stars in the centre of the picture form the belt of 
Orion. Just below, in the sword handle, is an irregular white patch about 
one-eighth of an inch in diameter. This is a small-scale image of the great 
nebula in Orion, shown on a larger scale in Fig. 2. 



THE NEW HEAVENS 



BY 

GEORGE ELLERY HALE 

DIRECTOR OF THE MOUNT WILSON OBSERVATORY OF THE CARNEGIE 
INSTITUTION OF WASHINGTON 



WITH 
NUMEROUS ILLUSTRATIONS 



NEW YORK 

CHARLES SCRIBNER'S SONS 
1922 






\ 2 



Copyright, 1920, 1921, 1922, by 
CHARLES SCRIBNER'S SONS 



Printed in the United States of America 



Published April, 1922 




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TO 

MY WIFE 



PREFACE 

Fourteen years ago, in a book entitled "The 
Study of Stellar Evolution" (University of Chi- 
cago Press, 1908), I attempted to give in untech- 
nical language an account of some modern methods 
of astrophysical research. This book is now out 
of print, and the rapid progress of science has left 
it completely out of date. As I have found no op- 
portunity to prepare a new edition, or to write an- 
other book of similar purpose, I have adopted the 
simpler expedient of contributing occasional articles 
on recent developments to Scribners Magazine, 
three of which are included in the present volume. 

I am chiefly indebted, for the illustrations, to the 
Mount Wilson Observatory and the present and 
former members of its staff whose names appear in 
the captions. Special thanks are due to Mr. Fer- 
dinand Ellerman, who made all of the photographs 
of the observatory buildings and instruments, and 
prepared all material for reproduction. The cut 
of the original Cavendish apparatus is copied from 
the Philosophical Transactions for i?q8 with the 
kind permission of the Royal Society, and I am 
also indebted to the Royal Society and to Profes- 
sor Fowler and Father Cortie for the privilege of 
reproducing from the Proceedings two illustrations 

of their spectroscopic results. p r „ 

\j. \L. ri. 

January, 1922. 



CONTENTS 

CHAPTER PAGE 

I. The New Heavens i 

II. Giant Stars 35 

III. Cosmic Crucibles 61 



ILLUSTRATIONS 

FIG. PAGE 

1. The Constellation of Orion (Hubble) Frontispiece 

2. The Great Nebula in Orion (Pease) 3 

3. Model by Ellerman of summit of Mount Wilson, show- 

ing the observatory buildings among the trees and 
bushes . . . . 5 

4. The 100-inch Hooker telescope 7 

5. Erecting the polar axis of the 100-inch telescope ... 9 

6. Lowest section of tube of 100-inch telescope, ready to 

leave Pasadena for Mount Wilson 11 

7. Section of a steel girder for dome covering the 100- 

inch telescope, on its way up Mount Wilson ... 13 

8. Erecting the steel building and revolving dome that 

cover the Hooker telescope 15 

9. Building and revolving dome, 100 feet in diameter, 

covering the 100-inch Hooker telescope 17 

10. One-hundred-inch mirror, just silvered, rising out of 

the silvering-room in pier before attachment to lower 

end of telescope tube. (Seen above) 19 

11. The driving-clock and worm-gear that cause the 100- 

inch Hooker telescope to follow the stars 21 

12. Large irregular nebula and star cluster in Sagittarius 

(Duncan) 22 

13. Faint spiral nebula in the constellation of the Hunt- 

ing Dogs (Pease) 23 

14. Spiral nebula in Andromeda, seen edge on (Ritchey) . 25 

[ xiii 1 



ILLUSTRATIONS 

FIG. PAGE 

15. Photograph of the moon made on September 15, 1919, 

with the 100-inch Hooker telescope (Pease) .... 28 

16. Photograph of the moon made on September 15, 1919, 

with the 100-inch Hooker telescope (Pease) .... 29 

17. Hubble's Variable Nebula. One of the few nebulae 

known to vary in brightness and form 31 

18. Ring Nebula in Lyra, photographed with the 60-inch 

(Ritchey) and 100-inch (Duncan) telescopes ... 32 

19. Gaseous prominence at the sun's limb, 140,000 miles 

high (Ellerman) 36 

20. The sun, 865,000 miles in diameter, from a direct 

photograph showing many sun-spots (Whitney) . . 37 

21. Great sun-spot group, August 8, 191 7 (Whitney) . . 39 

22. Photograph of the hydrogen atmosphere of the sun 

(Ellerman) 41 

23. Diagram showing outline of the 100-inch Hooker tele- 

scope, and path of the two pencils of light from a star 
when under observation with the 20-foot Michelson 
interferometer 45 

24. Twenty-foot Michelson interferometer for measuring 

star diameters, attached to upper end of the skeleton 
tube of the 100-inch Hooker telescope 47 

25. The giant Betelgeuse (within the circle), familiar as the 

conspicuous red star in the right shoulder of Orion 
(Hubble) 49 

26. Arcturus (within the white circle), known to the Arabs 

as the "Lance Bearer," and to the Chinese as the 
"Great Horn" or the "Palace of the Emperors" 
(Hubble) 51 

27. The giant star Antares (within the white circle), no- 

table for its red color in the constellation Scorpio, 
and named by the Greeks "A Rival of Mars" (Hub- 
ble) 54 



ILLUSTRATIONS 

FIO. PAGE 

28. Diameters of the Sun, Arcturus, Betelgeuse, and An- 

tares compared with the orbit of Mars 57 

29. Aldebaran, the "leader" (of the Pleiades), was also 

known to the Arabs as "The Eye of the Bull," "The 
Heart of the Bull," and "The Great Camel" (Hub- 
ble) 59 

30. Solar prominences, photographed with the spectro- 

heliograph without an eclipse (Ellerman) 63 

31. The 150-foot tower telescope of the Mount Wilson 

Observatory 65 

32. Pasadena Laboratory of the Mount Wilson Observa- 

tory 6y 

33. Sun-spot vortex in the upper hydrogen atmosphere 

(BeniofT) 69 

34. Splitting of spectrum lines by a magnetic field (Bab- 

cock) 71 

35. Electric furnace in the Pasadena Laboratory of the 

Mount Wilson Observatory 73 



36 

37 
38 

39 
40 

4i 



Titanium oxide in red stars 75 

Titanium oxide in sun-spots 75 

The Cavendish experiment 77 

The Trifld Nebula in Sagittarius (Ritchey) 81 

Spiral nebula in Ursa Major (Ritchey) 83 

Mount San Antonio as seen from Mount Wilson . . 85 



[ xv ' 



CHAPTER I 

THE NEW HEAVENS 

Go out under the open sky, on a clear and moon- 
less night, and try to count the stars. If your sta- 
tion lies well beyond the glare of cities, which is 
often strong enough to conceal all but the brighter 
objects, you will find the task a difficult one. Rang- 
ing through the six magnitudes of the Greek astrono- 
mers, from the brilliant Sirius to the faintest per- 
ceptible points of light, the stars are scattered in 
great profusion over the celestial vault. Their num- 
ber seems limitless, yet actual count will show that 
the eye has been deceived. In a survey of the 
entire heavens, from pole to pole, it would not be 
possible to detect more than from six to seven thou- 
sand stars with the naked eye. From a single view- 
point, even with the keenest vision, only two or 
three thousand can be seen. .So many of these are 
at the limit of visibility that Ptolemy's "Almagest," 
a catalogue of all the stars whose places were mea- 
sured with the simple instruments of the Greek 
astronomers, contains only 1,022 stars. 

Back of Ptolemy, through the speculations of the 
Greek philosophers, the mysteries of the Egyptian 
sun-god, and the observations of the ancient Chal- 
deans, the rich and varied traditions of astronomy 

[ 1 1 



THE NEW HEAVENS 

stretch far away into a shadowy past. All peoples, 
in the first stirrings of their intellectual youth, drawn 
by the nightly splendor of the skies and the cease- 
less motions of the planets, have set up some system 
of the heavens, in which the sense of wonder and 
the desire for knowledge were no less concerned than 
the practical necessities of life. The measurement 
of time and the needs of navigation have always 
stimulated astronomical research, but the intellec- 
tual demand has been keen from the first. Hippar- 
chus and the Greek astronomers of the Alexandrian 
school, shaking off the vagaries of magic and divina- 
tion, placed astronomy on a scientific basis, though 
the reaction of the Middle Ages caused even such a 
great astronomer as Tycho Brahe himself to revert 
for a time to the practice of astrology. 

EARLY INSTRUMENTS 

The transparent sky of Egypt, rarely obscured 
by clouds, greatly favored Ptolemy's observations. 
Here was prepared his great star catalogue, based 
upon the earlier observations of Hipparchus, and 
destined to remain alone in its field for more than 
twelve centuries, until Ulugh Bey, Prince of Samar- 
cand, repeated the work of his Greek predecessor. 
Throughout this period the stars were looked upon 
mainly as points of reference for the observation of 
planetary motions, and the instruments of observa- 
tion underwent little change. The astrolabe, which 
consists of a circle divided into degrees, with a rotat- 
ing diametral arm for sighting purposes, embodies 

[ 2 1 



THE NEW HEAVENS 

their essential principle. In its simple form, the 
astrolabe was suspended in a vertical plane, and the 
stars were observed by bringing the sights on the 




Fig. 2. The Great Nebula in Orion (Pease). 

Photographed with the ioo-inch telescope. This short-exposure photograph 
shows only the bright central part of the nebula. A longer exposure reveals 
a vast outlying region. 

movable diameter to bear upon them. Their alti- 
tude was then read off on the circle. Ultimately, 
the circle of the astrolabe, mounted with one of its 
diameters parallel to the earth's axis, became the 
armillary sphere, the precursor of our modern equa- 
torial telescope. Great stone quadrants fixed in the 
meridian were also employed from very early times. 

[3 1 



THE NEW HEAVENS 

Out of such furnishings, little modified by the lapse 
of centuries, was provided the elaborate instru- 
mental equipment of Uranibourg, the great observa- 
tory built by Tycho Brahe on the Danish island of 
Huen in 1576. In this "City of the Heavens," still 
dependent solely upon the unaided eye as a collector 
of starlight, Tycho made those invaluable observa- 
tions that enabled Kepler to deduce the true laws 
of planetary motion. But after all these centuries 
the sidereal world embraced no objects, barring an 
occasional comet or temporary star, that lay beyond 
the vision of the earliest astronomers. The concep- 
tions of the stellar universe, except those that ig- 
nored the solid ground of observation, were limited 
by the small aperture of the human eye. But the 
dawn of another age was at hand. 

The dominance of the sun as the central body of 
the solar system, recognized by Aristarchus of Samos 
nearly three centuries before the Christian era, but 
subsequently denied under the authority of Ptolemy 
and the teachings of the Church, was reaffirmed by 
the Polish monk Copernicus in 1543. Kepler's laws 
of the motions of the planets, showing them to re- 
volve in ellipses instead of circles, removed the last 
defect of the Copernican system, and left no room 
for its rejection. But both the world and the Church 
clung to tradition, and some visible demonstration 
was urgently needed. This was supplied by Galileo 
through his invention of the telescope. 

The crystalline lens of the human eye, limited by 
the iris to a maximum opening about one-quarter of 

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THE NEW HEAVENS 

an inch in diameter, was the only collector of star- 
light available to the Greek and Arabian astrono- 
mers. . Galileo's telescope, which in 1610 suddenly 
pushed out the boundaries of the known stellar uni- 
verse and brought many thousands of stars into 
range, had a lens about 2^4 inches in diameter. The 
area of this lens, proportional to the square of its 
diameter, was about eighty-one times that of the 
pupil of the eye. This great increase in the amount 
of light collected should bring to view stars down to 
magnitude 10.5, of which nearly half a million are 
known to exist. 

It is not too much to say that Galileo's telescope 
revolutionized human thought. Turned to the 
moon, it revealed mountains, plains, and valleys, 
while the sun, previously supposed immaculate in 
its perfection, was seen to be blemished with dark 
spots changing from day to day. Jupiter, shown to 
be accompanied by four encircling satellites, afforded 
a picture in miniature of the solar system, and 
strongly supported the Copernican view of its or- 
ganization, which was conclusively demonstrated by 
Galileo's discovery of the changing phases of Venus 
and the variation of its apparent diameter during its 
revolution about the sun. Galileo's proof of the 
Copernican theory marked the downfall of medi- 
evalism and established astronomy on a firm foun- 
dation. But while his telescope multiplied a hun- 
dredfold the number of visible stars, more than a 
century elapsed before the true possibilities of side- 
real astronomy were perceived. 

[6] 



THE NEW HEAVENS 

STRUCTURE OF THE UNIVERSE 

Sir William Herschel was the first astronomer to 
make a serious attack upon the problem of the struc- 



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ture of the stellar universe. In his first memoir on 
the "Construction of the Heavens," read before the 
Royal Society in 1784, he wrote as follows: 

[ 7] 



THE NEW HEAVENS 

"Hitherto the sidereal heavens have, not inade- 
quately for the purpose designed, been represented 
by the concave surface of a sphere in the centre of 
which the eye of an observer might be supposed to 
be placed. ... In future we shall look upon those 
regions into which we may now penetrate by means 
of such large telescopes, as a naturalist regards a rich 
extent of ground or chain of mountains containing 
strata variously inclined and directed as well as con- 
sisting of very different materials." 

On turning his 1 8-inch reflecting telescope to a 
part of the Milky Way in Orion, he found its whitish 
appearance to be completely resolved into small 
stars, not separately seen with his former telescopes. 
"The glorious multitude of stars of all possible 
sizes that presented themselves here to my view are 
truly astonishing; but as the dazzling brightness of 
glittering stars may easily mislead us so far as to 
estimate their number greater than it really is, I 
endeavored to ascertain this point by counting many 
fields, and computing from a mean of them, what a 
certain given portion of the Milky Way might con- 
tain." By this means, applied not only to the Milky 
Way but to all parts of the heavens, Herschel deter- 
mined the approximate number and distribution of 
all the stars within reach of his instrument. 

By comparing many hundred gauges or counts of 
stars visible in a field of about one-quarter of the 
area of the moon, Herschel found that the average 
number of stars increased toward the great circle 
which most nearly conforms with the course of the 



THE NEW HEAVENS 

Milky Way. Ninety degrees from this plane, at the 
pole of the Milky Way, only four stars, on the aver- 
age, were seen in the field of the telescope. In 
approaching the Milky Way this number increased 



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Fig. 5. Erecting the polar axis of the 100-inch telescope. 



slowly at first, and then more and more rapidly, un- 
til it rose to an average of 122 stars per field. 

These observations were made in the northern 
hemisphere, and subsequently Sir John Herschel, 
using his father's telescope at the Cape of Good 
Hope, found an almost exactly similar increase of 
apparent star density for the southern hemisphere. 
According to his estimates, the total number of stars 
in both hemispheres that could be seen distinctly 

[9] 



THE NEW HEAVENS 

enough to be counted in this telescope would proba- 
bly be about five and one-half millions. 

The Herschels concluded that "the stars of our 
firmament, instead of being scattered in all direc- 
tions indifferently through space, form a stratum of 
which the thickness is small, in comparison with its 
length and breadth; and in which the earth occupies 
a place somewhere about the middle of its thickness, 
between the point where it subdivides into two prin- 
cipal laminae inclined at a small angle to each other." 
This view does not difFer essentially from our modern 
conception of the form of the Galaxy; but as the 
Herschels were unable to see stars fainter than the 
fifteenth magnitude, it is evident that their conclu- 
sions apply only to a restricted region surrounding 
the solar system, in the midst of the enormously ex- 
tended sidereal universe which modern instruments 
have brought within our range. 

MODERN METHODS 

The remarkable progress of modern astronomy 
is mainly due to two great instrumental advances: 
the rise and development of the photographic tele- 
scope, and the application of the spectroscope to the 
study of celestial objects. These new and powerful 
instruments, supplemented by many accessories 
which have completely revolutionized observatory 
equipment, have not only revealed a vastly greater 
number of stars and nebulae: they have also rendered 
feasible observations of a type formerly regarded as 
impossible. The chemical analysis of a faint star 

[ 10] 



THE NEW HEAVENS 

is now so easy that it can be accomplished in a very 
short time — as quickly, in fact, as an equally com- 
plex substance can be analyzed in the laboratory. 
The spectroscope also measures a star's velocity, 




Fig. 6. Lowest section of tube of ico-inch telescope, ready 
to leave Pasadena for Mount Wilson. 



the pressure at different levels in its atmosphere, its 
approximate temperature, and now, by a new and 
ingenious method, its distance from the earth. It 
determines the velocity of rotation of the sun and 
of nebulae, the existence and periods of orbital revo- 
lution of binary stars too close to be separated by 
any telescope, the presence of magnetic fields in sun- 
spots, and the fact that the entire sun, like the earth, 
is a magnet. 

[ ii 1 



THE NEW HEAVENS 

Such new possibilities, with many others resulting 
from the application of physical methods of the most 
diverse character, have greatly enlarged the astrono- 
mer's outlook. He may now attack two great prob- 
lems: (i) The structure of the universe and the mo- 
tions of its constituent bodies, and (2) the evolution 
of the stars: their nature, origin, growth, and de- 
cline. These two problems are intimately related 
and must be studied as one.* 

If space permitted, it would be interesting to sur- 
vey the progress already accomplished by modern 
methods of astronomical research. Hundreds of 
millions of stars have been photographed, and the 
boundaries of the stellar universe have been pushed 
far into space, but have not been attained. Globu- 
lar star clusters, containing tens of thousands of 
stars, are on so great a scale (according to Shapley) 
that light, travelling at the rate of 186,000 miles per 
second, may take 500 years to cross one of them, 
while the most distant of these objects may be more 
than 200,000 light-years from the earth. The spiral 
nebulae, more than a million in number, are vast 
whirling masses in process of development, but we 
are not yet certain whether they should be regarded 
as " island universes" or as subordinate to the stellar 
system which includes our minute group of sun and 
planets, the great star clouds of the Milky Way, 
and the distant globular star clusters. 

These few particulars may give a slight concep- 

* A third great problem open to the astronomer, the study of 
the constitution of matter, is described in Chapter III. 

[ 12 ] 



THE NEW HEAVENS 

tion of the scale of the known universe, but a word 
must be added regarding some of its most striking 
phenomena. The great majority of the stars whose 
motions have been determined belong to one or the 







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Fig. 7. Section of a steel girder for dome covering the 100 
inch telescope, on its way up Mount Wilson. 



other of two great star streams, but the part played 
by these streams in the sidereal system as a whole 
is still obscure. The stars have been grouped in 
classes, presumably in the order of their evolutional 
development, as they pass from the early state of 
gaseous masses, of low density, through the succes- 
sive stages resulting from loss of heat by radiation 
and increased density due to shrinkage. Strangely 

[ 13 ] 



THE NEW HEAVENS 

enough, their velocities in space show a correspond- 
ing change, increasing as they grow older or perhaps 
depending upon their mass. 

It is impossible within these limits to do more than 
to give some indication of the scope of the new 
astronomy. Enough has been said, however, to 
assist in appreciating the increased opportunity for 
investigation, and the nature of the heavy demands 
made upon the modern observatory. But before 
passing on to describe one of the latest additions to 
the astronomer's instrumental equipment, a word 
should be added regarding the chief classes of tele- 
scopes. 

REFRACTORS AND REFLECTORS 

Astronomical telescopes are of two types: refrac- 
tors and reflectors. A refracting telescope consists 
of an object-glass composed of two or more lenses, 
mounted at the upper end of a tube, which is pointed 
at the celestial object. The light, after passing 
through the lenses, is brought to a focus at the lower 
end of the tube, where the image is examined visu- 
ally with an eyepiece, or photographed upon a sen- 
sitive plate. The largest instruments of this type 
are the 36-inch Lick telescope and the 40-inch re- 
fractor of the Yerkes Observatory. 

Reflecting telescopes, which are particularly 
adapted for photographic work, though also excel- 
lent for visual observations, are very differently con- 
structed. No lens is used. The telescope tube is 
usually built in skeleton form, open at its upper end, 

1 14] 



THE NEW HEAVENS 

and with a large concave mirror supported at its 
base. This mirror serves in place of a lens. Its 




Fig. 8. Erecting the steel building and revolving dome that 
cover the Hooker telescope. 

upper surface is paraboloidal in shape, as a spherical 
surface will not unite in a sharp focus the rays com- 

[ 15 1 



THE NEW HEAVENS 

ing from a distant object. The light passes through 
no glass — a great advantage, especially for photog- 
raphy, as the absorption in lenses cuts out much of 
the blue and violet light, to which photographic 
plates are most sensitive. The reflection occurs on 
the upper surface of the mirror, which is covered 
with a coat of pure silver, renewed several times a 
year and always kept highly burnished. Silvered 
glass is better than metals or other substances for 
telescope mirrors, chiefly because of the perfection 
with which glass can be ground and polished, and 
the ease of renewing its silvered surface when tar- 
nished. 

The great reflectors of Herschel and Lord Rosse, 
which were provided with mirrors of speculum 
metal, were far inferior to much smaller telescopes 
of the present day. With these instruments the 
star images were watched as they were carried 
through the field of view by the earth's rotation, or 
kept roughly in place by moving the telescope with 
ropes or chains. Photographic plates, which reveal 
invisible stars and nebulae when exposed for hours 
in modern instruments, were not then available. 
In any case they could not have been used, in the 
absence of the perfect mechanism required to keep 
the star images accurately fixed in place upon the 
sensitive film. 

It would be interesting to trace the long contest 
for supremacy between refracting and reflecting tele- 
scopes, each of which, at certain stages in its develop- 
ment, appeared to be unrivalled. In modern ob- 

[ 16 ] 



THE NEW HEAVENS 

servatories both types are used, each for the purpose 
for which it is best adapted. For the photograph}' 
of nebulae and the study of the fainter stars, the 
reflector has special advantages, illustrated by the 
work of such instruments as the Crosslev and Mills 




Fig. 9. Building and revolving dome. 100 feet in diameter, 
covering the 100-inch Hooker telescope. 

Photographed from the summit of the 150-foot-tower telescope. 



reflectors of the Lick Observatory; the great 72-inch 
reflector, recently brought into effective service at 
the Dominion Observatory in Canada; and the 60- 
inch and 100-inch reflectors of the Mount Wilson 
Observatory. 

The unaided eye, with an available area of one- 
twentieth of a square inch, permits us to see stars of 

[ 17 ] 



THE NEW HEAVENS 

the sixth magnitude. Herschel's 1 8-inch reflector, 
with an area 5,000 times as great, rendered visible 
stars of the fifteenth magnitude. The 60-inch reflec- 
tor, with an area 57,600 times that of the eye, re- 
veals stars of the eighteenth magnitude, while to 
reach stars of about the twentieth magnitude, pho- 
tographic exposures of four or five hours suffice with 
this instrument. 

Every gain of a magnitude means a great gain in 
the number of stars rendered visible. Stars of the 
second magnitude are 3.4 times as numerous as 
those of the first, those of the eighth magnitude are 
three times as numerous as those of the seventh, 
while the sixteenth magnitude stars are only 1.7 as 
numerous as those of the fifteenth magnitude. This 
steadily decreasing ratio is probably due to an actual 
thinning out of the stars toward the boundaries of 
the stellar universe, as the most exhaustive tests 
have failed to give any evidence of absorption of 
light in its passage through space. But in spite of 
this decrease, the gain of a single additional magni- 
tude may mean the addition of many millions of 
stars to the total of those already shown by the 60- 
inch reflector. Here is one of the chief sources of 
interest in the possibilities of a 100-inch reflecting 
telescope. 

IOO-INCH TELESCOPE 

In 1906 the late John D. Hooker, of Los Angeles, 
gave the Carnegie Institution of Washington a sum 
sufficient to construct a telescope mirror 100 inches 

[ 18 1 



THE NEW HEAVENS 

in diameter, and thus large enough to collect 160,000 
times the light received by the eye. (Fig. 10.) The 
casting and annealing of a suitable glass disk, 101 
inches in diameter and 13 inches thick, weighing 
four and one-half tons, was a most difficult opera- 




Fig. 10. One-hundred-inch mirror, just silvered, rising out of the 

silvering-room in pier before attachment to lower end of 

telescope tube. (Seen above.) 

tion, finally accomplished by a great French glass 
company at their factory in the Forest of St. Go- 
bain. A special optical laboratory was erected at 
the Pasadena headquarters of the Mount Wilson 
Observatory, and here the long task of grinding, 
figuring, and testing the mirror was successfully car- 
ried out by the observatory opticians. This opera- 

[ 19] 



THE NEW HEAVENS 

tion, which is one of great delicacy, required years 
for its completion. Meanwhile the building, dome, 
and mounting for the telescope were designed by 
members of the observatory staff, and the working 
drawings were prepared. An opportune addition by 
Mr. Carnegie to the endowment of the Carnegie 
Institution of Washington, of which the observatory 
is a branch, permitted the necessary appropriations 
to be made for the completion and erection of the 
telescope. Though delayed by the war, during 
which the mechanical and optical facilities of the 
observatory shops were utilized for military and 
naval purposes, the telescope is now in regular use 
on Mount Wilson. 

The instrument is mounted on a massive pier of 
reinforced concrete, 33 feet high and 52 feet in di- 
ameter at the top. A solid wall extends south from 
this pier a distance of 50 feet, on the west side of 
which a very powerful spectrograph, for photo- 
graphing the spectra of the brightest stars, will be 
mounted. Within the pier are a photographic dark 
room, a room for silvering the large mirror (which 
can be lowered into the pier), and the clock- room, 
where stands the powerful driving-clock, with which 
the telescope is caused to follow the apparent motion 
of the stars. (Fig. 11.) 

The telescope mounting is of the English type, in 
which the telescope tube is supported by the declina- 
tion trunnions between the arms of the polar axis, 
built in the form of a rectangular yoke carried by 
bearings on massive pedestals to the north and south. 

[ 20 1 



THE NEW HEAVENS 

These bearings must be aligned exactly parallel to 
the axis of the earth, and must support the polar 
axis so freely that it can be rotated with perfect pre- 
cision by the driving-clock, which turns a worm- 




Fig. II. The driving-clock and worm-gear that cause the ioo- 
inch Hooker telescope to follow the stars. 

wheel 17 feet in diameter, clamped to the lower end 
of the axis. As this motion must be sufficiently uni- 
form to counteract exactly the rotation of the earth 
on its axis, and thus to maintain the star images 
accurately in position in the field of view, the great- 
est care had to be taken in the construction of the 
driving-clock and in the spacing and cutting of the 
teeth in the large worm-wheel. Here, as in the case 

[ 21 ] 



THE NEW HEAVENS 

of all of the more refined parts of the instrument, 
the work was done by skilled machinists in the ob- 
servatory shops in Pasadena or on Mount Wilson 




Fig. 12. Large irregular nebula and star cluster in Sagittarius 
(Duncan). 

Photographed with the 6o-inch telescope. 

after the assembling of the telescope. The massive 
sections of the instrument, some of which weigh as 
much as ten tons each, were constructed at Quincy, 
Mass., where machinery sufficiently large to build 
battleships was available. They were then shipped 
to California, and transported to the summit of 

[ 22 ] 



THE NEW HEAVENS 

Mount Wilson over a road built for this purpose 
by the construction division of the observatory, 
which also built the pier on which the telescope 




Fig. 13. Faint spiral nebula in the constellation of the 

Hunting Dogs (Pease). 

Photographed with the 60-inch telescope. 

stands, and erected the steel building and dome that 
cover it. 

The parts of the telescope which are moved by 
the driving-clock weigh about ioo tons, and it was 
necessary to provide means of reducing the great 
friction on the bearings of the polar axis. To ac- 
complish this, large hollow steel cylinders, floating 
in mercury held in cast-iron tanks, were provided 
at the upper and lower ends of the polar axis. Al- 

[ 23 ] 



THE NEW HEAVENS 

most the entire weight of the instrument is thus 
floated in mercury, and in this way the friction is so 
greatly reduced that the driving-clock moves the 
instrument with perfect ease and smoothness. 

The ioo-inch mirror rests at the bottom of the 
telescope tube on a special support system, so de- 
signed as to prevent any bending of the glass under 
its own weight. Electric motors, forty in number, 
are provided to move the telescope rapidly or slowly 
in right ascension (east or west) and in declination 
(north or south), for focussing the mirrors, and for 
many other purposes. They are also used for ro- 
tating the dome, ioo feet in diameter, under which 
the telescope is mounted, and for opening the 
shutter, 20 feet wide, through which the observa- 
tions are made. 

A telescope of this kind can be used in several 
different ways. The 100-inch mirror has a focal 
length of about 42 feet, and in one of the arrange- 
ments of the instrument, the photographic plate is 
mounted at the centre of the telescope tube near its 
upper end, where it receives directly the image 
formed by the large mirror. In another arrange- 
ment, a silvered glass mirror, with plane surface, is 
supported near the upper end of the tube at an angle 
of 45 , so as to form the image at the side of the 
tube, where the photographic plate can be placed. 
In this case, the observer stands on a platform, 
which is moved up and down by electric motors in 
front of the opening in the dome through which the 
observations are made. 

[24] 



THE NEW HEAVENS 

Other arrangements of the telescope, for which 
auxiliary convex mirrors carried near the upper end 
of the tube are required, permit the image to be 
photographed at the side of the tube near its lower 




Fig. 14. Spiral nebula in Andromeda, seen edge on (Ritchey). 
Photographed with the 60-inch telescope. 



end, either with or without a spectrograph; or with 
a very powerful spectrograph mounted within a con- 
stant-temperature chamber south of the telescope 
pier. In this last case, the light of a star is so re- 
flected by auxiliary mirrors that it passes down 
through a hole in the south end of the polar axis and 
brings the star to a focus on the slit of the fixed 
spectrograph. 

[ 25 ] 



THE NEW HEAVENS 

ATMOSPHERIC LIMITATIONS 

The huge dimensions of such a powerful engine 
of research as the Hooker telescope are not in them- 
selves a source of satisfaction to the astronomer, 
for they involve a decided increase in the labor of 
observation and entail very heavy expense, justifi- 
able only in case important results, beyond the 
reach of other instruments, can be secured. The 
construction of a telescope of these dimensions was 
necessarily an experiment, for it was by no means 
certain, after the optical and mechanical difficulties 
had been overcome, that even the favorable atmos- 
phere of California would be sufficiently tranquil to 
permit sharply defined celestial images to be ob- 
tained with so large an aperture. It is therefore 
important to learn what the telescope will actually 
accomplish under customary observing conditions. 

Fortunately we are able to measure the perform- 
ance of the instrument with certainty. Close be- 
side it on Mount Wilson stands the 6o-inch reflector, 
of similar type, erected in 1908. The two telescopes 
can thus be rigorously compared under identical 
atmospheric conditions. 

The large mirror of the 100-inch telescope has 
an area about 2.8 times that of the 60-inch, and 
therefore receives nearly three times as much light 
from a star. Under atmospheric conditions perfect 
enough to allow all of this light to be concentrated 
in a point, it should be capable of recording on a 
photographic plate, with a given exposure, stars 

[ 26 1 



THE NEW HEAVENS 

about one magnitude fainter than the faintest stars 
within reach of the 6o-inch. The increased focal 
length, permitting such objects as the moon to be 
photographed on a larger scale, should also re- 
veal smaller details of structure and render pos- 
sible higher accuracy of measurement. Finally, the 
greater theoretical resolving power of the larger 
aperture, providing it can be utilized, should permit 
the separation of the members of close double stars 
beyond the range of the smaller instrument. 

CRITICAL TESTS 

The many tests already made indicate that the 
advantages expected of the new telescope will be 
realized in practice. The increased light-gathering 
power will mean the addition of many millions of 
stars to those already known. Spectroscopic ob- 
servations now in regular progress have carried the 
range of these investigations far beyond the possi- 
bilities of the 6oinch telescope. A great class of 
red stars, for example, almost all the members of 
which were inaccessible to the 6o-inch, are now being 
made the subject of special study. And in other 
fields of research equal advantages have been gained. 

The increase in the scale of the images over those 
given by the 6o-inch telescope is illustrated by two 
photographs of the Ring Nebula in Lyra, reproduced 
in Fig. 1 8. The Great Nebula in Orion, photo- 
graphed with the ioo-inch telescope with a com- 
paratively short exposure, sufficient to bring out 
the brighter regions, is reproduced in Fig. 2. It is 

[ 27] 




•>W .} 



w&5 ; 





Fig. 15. Photograph of the moon made on September 15, 1919. 
with the 100-inch Hooker telescope (Pease). 

The ring-like formations are the so-called craters, most of them far larger than 
anything similar on the earth. That in the lower left corner with an isolated 
mountain in the centre is Albategnius. sixty-four miles in diameter. Peaks 
in the ring rise to a height of fifteen thousand feet above the central plain. 
Xote the long sunset shadows cast by the mountains on the left. The level 
region below on the right is an extensive plain, the Mare Xubium. 




Fig. 16. Photograph of the moon made on September 15, 1919, 
with the 100-inch Hooker telescope (Pease). 

The mountains above and to the left are the lunar Apennines; those on the left 
just below the centre are the Alps. Both ranges include peaks from fifteen 
thousand to twenty thousand feet in height. In the upper right corner is 
Copernicus, about fifty miles in diameter. The largest of the conspicuous 
group of three just below the Apennines is Archimedes and at the lower end 
of the Alps is Plato. Note the long sunset shadows cast by the isolated 
peaks on the left. The central portion of the picture is a vast plain, the 
Mare Imbrium. 



THE NEW HEAVENS 

interesting to compare this picture with the small- 
scale image of the same nebula shown in Fig. I. 

The sharpness of the images given by the new 
telescope may be illustrated by some recent photo- 
graphs of the moon, obtained with an equivalent 
focal length of 134 feet. In Fig. 15 is shown a 
rugged region of the moon, containing many ring- 
like mountains or craters. Fig. 16 shows the great 
arc of the lunar Apennines (above) and the Alps 
(below), to the left of the broad plain of the Mare 
Imbrium. The starlike points along the moon's 
terminator, which separates the dark area from the 
region upon which the sun (on the right) shines, are 
the mountain peaks, about to disappear at sunset. 
The long shadows cast by the mountains just with- 
in the illuminated area are plainly seen. Some of 
the peaks of the lunar Apennines attain a height of 
20,000 feet. 

In less powerful telescopes the stars at the centre 
of the great globular clusters are so closely crowded 
together that they cannot be studied separately with 
the spectrograph. Moreover, most of them are much 
too faint for examination with this instrument. At 
the 1 3 4- foot focus the 100-inch telescope gives a 
large-scale image of such clusters, and permits the 
spectra of stars as faint as the fifteenth magnitude 
to be separately photographed. 

CLOSE DOUBLE STARS 

A remarkable use of the 100-inch telescope, which 
permits its full theoretical resolving power to be not 

[30] 



THE NEW HEAVENS 

merely attained but to be doubled, has been made 
possible by the first application of Michelson's inter- 




Fig. 17. Hubble's Variable Nebula. One of the few nebulae 

known to vary in brightness and form. 

Photographed with the 100-inch telescope (Hubble). 

ference method to the measurement of very close 
double stars. When employing this, the ioo-inch 
mirror is completely covered, except for two slits. 

[ 31 ] 



THE NEW HEAVENS 

Beams of light from a star, entering by the slits, 
unite at the focus of the telescope, where the image 
is examined by an eyepiece magnifying about five 
thousand diameters. Across the enlarged star image 
a series of fine, sharp fringes is seen, even when the 
atmospheric conditions are poor. If the star is 




Fig. 1 8. Ring Nebula in Lyra, photographed with the 6o-inch 
(Ritchey) and ioo-inch (Duncan) telescopes. 

Showing the increased scale of the images given by the larger instrument. 

single the fringes remain visible, whatever the dis- 
tance between the slits. But in the case of a star 
like Capella, previously inferred to be double from 
the periodic displacement of the lines in its spec- 
trum, but with components too close together to be 
distinguished separately, the fringes behave differ- 
ently. As the slits are moved apart a point is 
reached where the fringes completely disappear, 
only to reappear as the separation is continued. 
This effect is obtained when the slits are at right 

[ 32 ] 



THE NEW HEAVENS 

angles to the line joining the two stars of the pair, 
found by this method to be 0.0418 of a second of arc 
apart (on December 30, 1919). Subsequent mea- 
sures, of far greater precision than those obtainable 
by other methods in the case of easily separated 
double stars, show the rapid orbital motion of the 
components of the system. This device will be ap- 
plied to other close binaries, hitherto beyond the 
reach of measurement. 

Without entering into further details of the tests, 
it is evident that the new telescope will afford 
boundless possibilities for the study of the stellar 
universe.* The structure and extent of the galactic 
system, and the motions of the stars comprising it; 
the distribution, distances, and dimensions of the 
spiral nebulae, their motions, rotation, and mode of 
development; the origin of the stars and the succes- 
sive stages in their life history: these are some of the 
great questions which the new telescope must help 
to answer. In such an embarrassment of riches the 
chief difficulty is to withstand the temptation toward 
scattering of effort, and to form an observing pro- 
gramme directed toward the solution of crucial 
problems rather than the accumulation of vast 
stores of miscellaneous data. This programme will 
be supplemented by an extensive study of the sun, 
the only star near enough the earth to be examined 
in detail, and by a series of laboratory investigations 

* It is not adapted for work on the sun, as the mirrors would be 
distorted by its heat. Three other telescopes, especially designed 
for solar observations, are in use on Mount Wilson. 

[33 ] 



THE NEW HEAVENS 

involving the experimental imitation of solar and 
stellar conditions, thus aiding in the interpretation 
of celestial phenomena. 



34 



CHAPTER II 
GIANT STARS 

Our ancestral sun, as pictured by Laplace, origi- 
nally extended in a state of luminous vapor beyond 
the boundaries of the solar system. Rotating upon 
its axis, it slowly contracted through loss of heat by 
radiation, leaving behind it portions of its mass, 
which condensed to form the planets. Still gaseous, 
though now denser than water, it continues to pour 
out the heat on which our existence depends, as it 
shrinks imperceptibly toward its ultimate condition 
of a cold and darkened globe. 

Laplace's hypothesis has been subjected in recent 
years to much criticism, and there is good reason to 
doubt whether his description of the mode of evolu- 
tion of our solar system is correct in every particular. 
All critics agree, however, that the sun was once 
enormously larger than it now is, and that the plan- 
ets originally formed part of its distended mass. 

Even in its present diminished state, the sun is 
huge beyond easy conception. Our own earth, 
though so minute a fragment of the primeval sun, 
is nevertheless so large that some parts of its sur- 
face have not yet been explored. Seen beside the 

[35 1 



THE NEW HEAVENS 

sun, by an observer on one of the planets, the earth 
would appear as an insignificant speck, which could 
be swallowed with ease by the whirling vortex of a 
sun-spot. If the sun were hollow, with the earth 




Fig. 19. Gaseous prominence at the sun's limb, 140,000 miles 
high (Ellerman). 

Photographed with the spectroheliograph, using the light emitted by glowing 
calcium vapor. The comparative size of the earth is indicated by the 
white circle. 



at its centre, the moon, though 240,000 miles from 
us, would have room and to spare in which to de- 
scribe its orbit, for the sun is 865,000 miles in 
diameter, so that its volume is more than a million 
times that of the earth. 

But w T hat of the stars, proved by the spectroscope 
to be self-luminous, intensely hot, and formed of the 

[ 36] 



GIANT STARS 

same chemical elements that constitute the sun and 
the earth ? Are they comparable in size with the 
sun ? Do they occur in all stages of development, 




Fig. 20. The sun, 865,000 miles in diameter, from a direct 
photograph showing many sun-spots (Whitney) 

The small black disk in the centre represents the comparative size of the earth, 
while the circle surrounding it corresponds in diameter to the orbit of the 
moon. 



from infancy to old age ? And if such stages can be 
detected, do they afford indications of the gradual 
diminution in volume which Laplace imagined the 
sun to experience ? 

[ 37] 



THE NEW HEAVENS 

STAR IMAGES 

Prior to the application of the powerful new en- 
gine of research described in this article we have had 
no means of measuring the diameters of the stars. 
We have measured their distances and their mo- 
tions, determined their chemical composition, and 
obtained undeniable evidence of progressive devel- 
opment, but even in the most powerful telescopes 
their images are so minute that they appear as points 
rather than as disks. In fact, the larger the tele- 
scope and the more perfect the atmospheric condi- 
tions at the observer's command, the smaller do 
these images appear. On the photographic plate, 
it is true, the stars are recorded as measurable 
disks, but these are due to the spreading of the 
light from their bright point-like images, and their 
diameters increase as the exposure time is prolonged. 
From the images of the brighter stars rays of light 
project in straight lines, but these also are instru- 
mental phenomena, due to diffraction of light by 
the steel bars that support the small mirror in the 
tube of reflecting telescopes. In a word, the stars 
are so remote that the largest and most perfect 
telescopes show them only as extremely minute 
needle-points of light, without any trace of their 
true disks. 

How, then, may we hope to measure their diame- 
ters ? By using, as the man of science must so often 
do, indirect means when the direct attack fails. 
Most of the remarkable progress of astronomy dur- 

[ 38 ] 



GIANT STARS 

ing the last quarter-century has resulted from the 
application of new and ingenious devices borrowed 
from the physicist. These have multiplied to such 
a degree that some of our observatories are literally 



r 



Fig. 21. Great sun-spot group, August 8, 19 17 (Whitney). 

The disk in the corner represents the comparative size of the earth. 

physical laboratories, in which the sun and stars are 
examined by powerful spectroscopes and other opti- 
cal instruments that have recently advanced our 
knowledge of physics by leaps and bounds. In the 
present case we are indebted for our star-measuring 
device to the distinguished physicist Professor Al- 
bert A. Michelson, who has contributed a long array 

[ 39 ] 



THE NEW HEAVENS 

of novel apparatus and methods to physics and 
astronomy. 

THE INTERFEROMETER 

The instrument in question, known as the inter- 
ferometer, had previously yielded a remarkable se- 
ries of results when applied in its various forms to 
the solution of fundamental problems. To mention 
only a few of those that have helped to establish 
Michelson's fame, we may recall that our exact 
knowledge of the length of the international metre 
at Sevres, the world's standard of measurement, was 
obtained by him with an interferometer in terms of 
the invariable length of light-weaves. A different 
form of interferometer has more recently enabled 
him to measure the minute tides within the solid 
body of the earth — not the great tides of the ocean, 
but the slight deformations of the earth's body, 
which is as rigid as steel, that are caused by the 
varying attractions of the sun and moon. Finally, 
to mention only one more case, it was the Michelson- 
Morley experiment, made years ago with still an- 
other form of interferometer, that yielded the basic 
idea from which the theory of relativity was devel- 
oped by Lorentz and Einstein. 

The history of the method of measuring star 
diameters is a very curious one, showing how the 
most promising opportunities for scientific progress 
may lie unused for decades. The fundamental 
principle of the device w T as first suggested by the 
great French physicist Fizeau in 1868. In 1874 trie 

[ 40] 



GIANT STARS 

theory was developed by the French astronomer 
Stephan, who observed interference fringes given by 
a large number of stars, and rightly concluded that 




Fig. 22. Photograph of the hydrogen atmosphere of the sun 
(Ellerman). 

Made with the spectroheliograph, showing the immense vortices, or whirling 
storms like tornadoes, that centre in sun-spots. The comparative size of 
the earth is shown by the white circle traced on the largest sun-spot. 



their angular diameters must be much smaller than 
0.158 of a second of arc, the smallest measurable with 
his instrument. In 1890 Michelson, unaware of 
the earlier work, published in the Philosophical 
Magazine a complete description of an interferometer 

[ 41 1 



THE NEW HEAVENS 

capable of determining with surprising accuracy the 
distance between the components of double stars so 
close together that no telescope can separate them. 
He also showed how the same principle could be 
applied to the measurement of star diameters if a 
sufficiently large interferometer could be built for 
this purpose, and developed the theory much more 
completely than Stephan had done. A year later 
he measured the diameters of Jupiter's satellites by 
this means at the Lick Observatory. But nearly 
thirty years elapsed before the next step was taken. 
Two causes have doubtless contributed to this de- 
lay. Both theory and experiment have demon- 
strated the extreme sensitiveness of the "interfer- 
ence fringes," on the observation of which the 
method depends, and it was generally supposed by 
astronomers that disturbances in the earth's atmos- 
phere would prevent them from being clearly seen 
with large telescopes. Furthermore, a very large 
interferometer, too large to be carried by any exist- 
ing telescope, was required for the star-diameter 
work, though close double stars could have been 
easily studied by this device with several of the large 
telescopes of the early nineties. But whatever the 
reasons, a powerful method of research lay unused. 
The approaching completion of the ioo-inch tele- 
scope of the Mount Wilson Observatory led me to 
suggest to Professor Michelson, before the United 
States entered the war, that the method be thor- 
oughly tested under the favorable atmospheric con- 
ditions of Southern California. He was at that 

[42 ] 



GIANT STARS 

time at work on a special form of interferometer, 
designed to determine whether atmospheric dis- 
turbances could be disregarded in planning large- 
scale experiments. But the war intervened, and 
all of our efforts were concentrated for two years on 
the solution of war problems.* In 1919, as soon as 
the 100-inch telescope had been completed and 
tested, the work was resumed on Mount Wilson. 

A LABORATORY EXPERIMENT 

The principle of the method can be most readily 
seen by the aid of an experiment which any one can 
easily perform for himself with simple apparatus. 
Make a narrow slit, a few thousandths of an inch in 
width, in a sheet of black paper, and support it verti- 
cally before a brilliant source of light. Observe 
this from a distance of 40 or 50 feet with a small 
telescope magnifying about 30 diameters. The 
object-glass of the telescope should be covered with 
an opaque cap, pierced by two circular holes about 
one-eighth of an inch in diameter and half an inch 
apart. The holes should be on opposite sides of the 
centre of the object-glass and equidistant from it, 
and the line joining the holes should be horizontal. 
When this cap is removed the slit appears as a 
narrow vertical band with much fainter bands on 
both sides of it. With the cap in place, the central 
bright band appears to be ruled with narrow vertical 

* Professor Michelson's most important contribution during 
the war period was a new and very efficient form of range-finder, 
adopted for use by the U. S. Navy. 

[ 43 ] 



THE NEW HEAVENS 

lines or fringes produced by the "interference" * of 
the two pencils of light coming through different 
parts of the object-glass from the distant slit. 
Cover one of the holes, and the fringes instantly dis- 
appear. Their production requires the joint effect 
of the two light-pencils. 

Now suppose the two holes over the object-glass 
to be in movable plates, so that their distance apart 
can be varied. As they are gradually separated the 
narrow vertical fringes become less and less distinct, 
and finally vanish completely. Measure the dis- 
tance between the holes and divide this by the wave- 
length of light, which we may call 50000 of an inch. 
The result is the angular width of the distant slit. 
Knowing the distance of the slit, we can at once 
calculate its linear width. If for the slit we substi- 
tute a minute circular hole, the method of measure- 
ment remains the same, but the angular diameter as 
calculated above must be multiplied by i.22.f 

To measure the diameter of a star we proceed in 
a similar way, but, as the angle it subtends is so 
small, we must use a very large telescope, for the 
smaller the angle the farther apart must be the two 
holes over the object-glass (or the mirror, in case a 
reflecting telescope is employed). In fact, when the 
holes are moved apart to the full aperture of the 

* For an explanation of the phenomena of interference, see any 
encyclopaedia or book on physics. 

t More complete details may be found in Michelson's Lowell 
Lectures on "Light-Waves and Their Uses," University of 
Chicago Press, 1907. 

[ 44] 



GIANT STARS 

ioo-inch Hooker telescope, the interference fringes 
are still visible even with the star Betelgeuse, though 
its angular diameter is perhaps as great as that of 
any other star. Thus, we must build an attach- 




Fig. 23. Diagram showing outline of the 100-inch Hooker tele- 
scope, and path of the two pencils of light from a star when 
under observation with the 20-foot Michelson interferometer. 

A photograph of the interferometer is shown in Fig. 24. 

ment for the telescope, so arranged as to permit us 
to move the openings still farther apart. 

THE 20-FOOT INSTRUMENT 

The 20-foot interferometer designed by Messrs. 
Michelson and Pease, and constructed in the Mount 
Wilson Observatory instrument-shop, is shown in 
the diagram (Fig. 23) and in a photograph of the 

[45 1 



THE NEW HEAVENS 

upper end of the skeleton tube of the telescope 
(Fig. 24). The light from the star is received by two 
flat mirrors (M 1 , M 4 ) which project beyond the tube 
and can be moved apart along the supporting arm. 
These take the place of the two holes over the object- 
glass in our experiment. From these mirrors the 
light is reflected to a second pair of flat mirrors 
(M 2 , M 3 ), which send it toward the 100-inch con- 
cave mirror (M 5 ) at the bottom of the telescope tube. 
After this the course of the light is exactly as it 
would be if the mirrors M 2 , M 3 were replaced by two 
holes over the 100-inch mirror. It is reflected to 
the convex mirror (M 6 ), then back in a less rapidly 
convergent beam toward the large mirror. Before 
reaching it the light is caught by the plane mirror 
(M 7 ) and reflected through an opening at the side 
of the telescope tube to the eye-piece E, Here the 
fringes are observed with a magnification ranging 
from 1,500 to 3,000 diameters. 

In the practical application of this method to the 
measurement of star diameters, the chief problem 
was whether the atmosphere would be quiet enough 
to permit sharp interference fringes to be produced 
with light-pencils more than 100 inches apart. 
After successful preliminary tests with the 40-inch 
refracting telescope of the Yerkes Observatory, Pro- 
fessor Michelson made the first attempt to see the 
fringes with the 60-inch and 100-inch reflectors on 
Mount Wilson in September, 1919. He was sur- 
prised and delighted to find that the fringes were 
perfectly sharp and distinct with the full aperture 

[ 46] 



GIANT STARS 

of both these instruments. Doctor Anderson, of 
the observatory staff, then devised a special form 
of interferometer for the measurement of close 
double stars, and applied it with the ioo-inch tele- 



SRr"~#!7T '# * # $##, b mm* **# $ ' J^ 




r- ^ = '' 
1'^ 


efclifipp.- 


^'•^^^^ 



Fig. 24. Twenty-foot Michelson interferometer for measuring 

star diameters, attached to upper end of the skeleton 

tube of the 100-inch Hooker telescope. 

The path of the two pencils of light from the star is shown in Fig. 23. For 
a photograph of the entire telescope, see Fig. 4. 



scope to the measurement of the orbital motion of 
the close components of Capella, with results of 
extraordinary accuracy, far beyond anything at- 
tainable by previous methods. The success of this 
work strongly encouraged the more ambitious proj- 
ect of measuring the diameter of a star, and the 
20-foot interferometer was built for this purpose. 

[47] 



THE NEW HEAVENS 

The difficult and delicate problem of adjusting the 
mirrors of this instrument with the necessary ex- 
treme accuracy was solved by Professor Michelson 
during his visit to Mount Wilson in the summer of 
1920, and with the assistance of Mr. Pease, of the 
observatory staff, interference fringes were observed 
in the case of certain stars when the mirrors were as 
much as 18 feet apart. All was thus in readiness 
for a decisive test as soon as a suitable star presented 
itself. 

THE GIANT BETELGEUSE 

Russell, Shapley, and Eddingtor had pointed out 
Betelgeuse (Arabic for "the giant's shoulder"), the 
bright red star in the constellation of Orion (Fig. 
25), as the most favorable of all stars for measure- 
ment, and the last-named had given its angular 
diameter as 0.051 of a second of arc. This deduction 
from theory appeared in his recent presidential ad- 
dress before the British Association for the Advance- 
ment of Science, in which Professor Eddington re- 
marked: "Probably the greatest need of stellar 
astronomy at the present day, in order to make sure 
that our theoretical deductions are starting on the 
right lines, is some means of measuring the apparent 
angular diameter of stars." He then referred to the 
work already in progress on Mount Wilson, but 
anticipated "that atmospheric disturbance will ulti- 
mately set the limit to what can be accomplished." 

On December 13, 1920, Mr. Pease successfully 
measured the diameter of Betelgeuse with the 20- 

[48 ] 




Fig. 25. The giant Betelgeuse (within the circle), familiar as the 
conspicuous red star in the right shoulder of Orion (Hubble). 

Measures with the interferometer show its angular diameter to be 0.047 of a sec- 
ond of arc, corresponding to a linear diameter of 215,000,000 miles, if the 
best available determination of its distance can be relied upon. This de- 
termination shows Betelgeuse to be 160 light-years from the earth. Light 
travels at the rate of 186,000 miles per second, and yet spends 160 years on 
its journey to us from this star. 



THE NEW HEAVENS 

foot interferometer. As the outer mirrors were 
separated the interference fringes gradually became 
less distinct, as theory requires, and as Doctor 
Merrill had previously seen when observing Betel- 
geuse with the interferometer used for Capella. At 
a separation of 10 feet the fringes disappeared com- 
pletely, giving the data required for calculating the 
diameter of the star. To test the perfection of the 
adjustment, the telescope was turned to other stars, 
of smaller angular diameter, which showed the 
fringes with perfect clearness. Turning back to 
Betelgeuse, they were seen beyond doubt to be ab- 
sent. Assuming the mean wave-length of the light 
of this star to be Too~of wo of a millimetre, its angular 
diameter comes out* 0.047 of a second of arc, thus 
falling between the values- — 0.051 and 0.031 of a 
second — predicted by Eddington and Russell from 
slightly different assumptions. Subsequent correc- 
tions and repeated measurement will change Mr. 
Pease's result somewhat, but it is almost certainly 
within 10 or 15 per cent of the truth. We may there- 
fore conclude that the angular diameter of Betel- 
geuse is very nearly the same as that of a ball 
one inch in diameter, seen at a distance of seventy 
miles. 

But this represents only the angle subtended by 
the star's disk. To learn its linear diameter, we 
must know its distance. Four determinations of the 
parallax, which determines the distance, have been 
made. Elkin, with the Yale heliometer, obtained 
0.032 of a second of arc. Schlesinger, from photo- 

[ So ] 



GIANT STARS 

graphs taken with the 30-inch Allegheny refractor, 
derived 0.016. Adams, by his spectroscopic method 




Fig. 26. Arcturus (within the white circle), known to the Arabs 

as the "Lance Bearer," and to the Chinese as the "Great 

Horn" or the "Palace of the Emperors" (Hubble). 

Its angular diameter, measured at Mount Wilson by Pease with the 20-foot 
Michelson interferometer on April 15, 1921, is 0.022 of a second, in close 
agreement with Russell's predicted value of 0.019 of a second. The mean 
parallax of Arcturus, based upon several determinations, is 0.095 of a second, 
corresponding to a distance of 34 light-years. The linear diameter, com- 
puted from Pease's measure and this value of the distance is about 21 mil- 
lion miles. 

applied with the 6o-inch Mount Wilson reflector, 
obtained 0.012. Lee's recent value, secured photo- 

[ Si ] 



THE NEW HEAVENS 

graphically with the 40-inch Yerkes refractor, is 0.022. 
The heliometer parallax is doubtless less reliable 
than the photographic ones, and Doctor Adams 
states that the spectral type and luminosity of Betel- 
geuse make his value less certain than in the case 
of most other stars. If we take a (weighted) mean 
value of 0.020 of a second, we shall probably not be 
far from the truth. This parallax represents the 
angle subtended by the radius of the earth's orbit 
(93,000,000 miles) at the distance of Betelgeuse. 
By comparing it with 0.047, the angular diameter 
of the star, we see that the linear diameter is about 
two and one-third times as great as the distance 
from the earth to the sun, or approximately 215,- 
000,000 miles. Thus, if this measure of its distance 
is not considerably in error, Betelgeuse would nearly 
fill the orbit of Mars. All methods of determining 
the distances of the stars are subject to uncertainty, 
however, and subsequent measures may reduce this 
figure very appreciably. But there can be no doubt 
that the diameter of Betelgeuse exceeds 100,000,000 
miles, and it is probably much greater. 

The extremely small angle subtended by this 
enormous disk is explained by the great distance of 
the star, which is about 160 light-years. That is to 
say, light travelling at the rate of 186,000 miles per 
second spends 160 years in crossing the space that 
lies between us and Betelgeuse, whose tremendous 
proportions therefore seem so minute even in the 
most powerful telescopes. 

[52 ] 



GIANT STARS 



STELLAR EVOLUTION 



This actual measure of the diameter of Betelgeuse 
supplies a new and striking test of Russell's and 
Hertzsprung's theory of dwarf and giant stars. 
Just before the war Russell showed that our old 
methods of classifying the stars according to their 
spectra must be radically changed. Stars in an 
early stage of their life history may be regarded as 
diffuse gaseous masses, enormously larger than our 
sun, and at a much lower temperature. Their 
density must be very low, and their state that of a 
perfect gas. These are the "giants." In the slow 
process of time they contract through constant 
loss of heat by radiation. But, despite this loss, 
the heat produced by contraction and from other 
sources (see p. 82) causes their temperature to rise, 
while their color changes from red to bluish white. 
The process of shrinkage and rise of temperature 
goes on so long as they remain in the state of a per- 
fect gas. But as soon as contraction has increased 
the density of the gas beyond a certain point the 
cycle reverses and the temperature begins to fall. 
The bluish-white light of the star turns yellowish, 
and we enter the dwarf stage, of which our own sun 
is a representative. The density increases, surpass- 
ing that of water in the case of the sun, and going 
far beyond this point in later stages. In the lapse 
of millions of years a reddish hue appears, finally 
turning to deep red. The falling temperature per- 

[ S3 1 



THE NEW HEAVENS 

mits the chemical elements, existing in a gaseous 

state in the outer atmosphere of the star, to unite 

^into compounds, which are rendered conspicuous by- 




Fig. 27. The giant star Antares (within the white circle), notable 

for its red color in the constellation Scorpio, and named 

by the Greeks "A Rival of Mars" (Hubble). 

The distance of Antares, though not very accurately known, is probably not far 
from 350 light-years. Its angular diameter of 0.040 of a second would thus 
correspond to a linear diameter of about 400 million miles. 

their characteristic bands in the spectrum. Finally 
comes extinction of light, as the star approaches its 
ultimate state of a cold and solid globe. 

We may thus form a new picture of the two 
branches of the temperature curve, long since sug- 

[ 54 1 



GIANT STARS 

gested by Lockyer, on very different grounds, as the 
outline of stellar life. On the ascending side are 
the giants, of vast dimensions and more diffuse than 
the air we breathe. There are good reasons for 
believing that the mass of Betelgeuse cannot be 
more than ten times that of the sun, while its volume 
is at least a million times as great and may exceed 
eight million times the sun's volume. Therefore, 
its average density must be like that of an atten- 
uated gas in an electric vacuum tube. Three- 
quarters of the naked-eye stars are in the giant 
stage, which comprises such familiar objects as 
Betelgeuse, Antares, and Aldebaran, but most of 
them are much denser than these greatly inflated 
bodies. The pinnacle is reached in the intensely hot 
white stars of the helium class, in whose spectra the 
lines of this gas are very conspicuous. The density 
of these stars is perhaps one-tenth that of the sun. 
Sirius, also very hot, is nearly twice as dense. Then 
comes the cooling stage, characterized, as already 
remarked, by increasing density, and also by increas- 
ing chemical complexity resulting from falling tem- 
perature. This life cycle is probably not followed 
by all stars, but it may hold true for millions of 
them. 

The existence of giant and dwarf stars has beer 
fully proved by the remarkable work of Adams and 
his associates on Mount Wilson, where his method 
of determining a star's distance and intrinsic lumi- 
nosity by spectroscopic observations has already 
been applied to 2,000 stars. Discussion of the re- 

[ ss 1 



THE NEW HEAVENS 

suits leads at once to the recognition of the two 
great classes of giants and dwarfs. Now comes the 
work of Michelson and Pease to cap the climax, giv- 
ing us the actual diameter of a typical giant star, in 
close agreement with predictions based upon theory. 
From this diameter we may conclude that the 
density of Betelgeuse is extremely low, in harmony 
with Russell's theory, which is further supported 
by spectroscopic analysis of the star's light, reveal- 
ing evidence of the comparatively low temperature 
called for by the theory at this early stage of stellar 
existence. 

TWO OTHER GIANTS 

The diameter of Arcturus was successfully mea- 
sured by Mr. Pease at Mount Wilson on April 15. 
As the mirrors of the interferometer were moved 
apart, the fringes gradually decreased in visibility 
until they finally disappeared at a mirror separation 
of 19.6 feet. Adopting a mean wave-length of 
T o^lHro to of a millimetre for the light of Arcturus, 
this gives a value of 0.022 of a second of arc for the 
angular diameter of the star. If we use a mean 
value of 0.095 °f a second for the parallax, the corre- 
sponding linear diameter comes out 21,000,000 miles. 
The angular diameter, as in the case of Betelgeuse, 
is in remarkably close agreement with the diameter 
predicted from theory. Antares, the third star mea- 
sured by Mr. Pease, is the largest of all. If it is 
actually a member of the Scorpius-Centaurus group, 
as we have strong reason to believe, it is fully 350 

1 56] 



GIANT STARS 

light-years from the earth, and its diameter is about 
400,000,000 miles. 



QR S1T . DF MAn S 



Fig. 28. Diameters of the Sun, Arcturus, Betelgeuse, and Antares 
compared with the orbit of Mars. 
. Sun, diameter, 865,000 miles. 

I Arcturus, diameter, 21,000,000 miles. 

. j Betelgeuse, diameter, 215,000,000 miles. 

Antares, diameter, 400,000,000 miles. 

It now remains to make further measures of Betel- 
geuse, especially because its marked changes in 
brightness suggest possible variations in diameter. 

1 57] 



THE NEW HEAVENS 

We must also apply the interferometer method to 
stars of the various spectral types, in order to afford 
a sure basis for future studies of stellar evolution. 
Unfortunately, only a few giant stars are certain to 
fall within the range of our present instrument. An 
interferometer of 70-feet aperture would be needed 
to measure Sirius accurately, and one of twice this 
size to deal with less brilliant white stars. A 100- 
foot instrument, if feasible to build, would permit 
objects representing most of the chief stages of 
stellar development to be measured, thus contrib- 
uting in the highest degree to the progress of our 
knowledge of the life history of the stars. Fortu- 
nately, though the mechanical difficulties are great, 
the optical problem is insignificant, and the cost of 
the entire apparatus, though necessarily high, would 
be only a small fraction of that of a telescope of cor- 
responding aperture, if such could be built. A 100- 
foot interferometer might be designed in many dif- 
ferent forms, and one of these may ultimately be 
found to be within the range of possibility. Mean- 
while the 20-foot interferometer has been improved 
so materially that it now promises to yield approx- 
imate measures of stars at first supposed to be be- 
yond its capacity. 

While the theory of dwarf and giant stars and the 
measurements just described afford no direct evi- 
dence bearing on Laplace's explanation of the forma- 
tion of planets, they show that stars exist which are 
comparable in diameter with our solar system, and 
suggest that the sun must have shrunk from vast 

[ 58 ] 




Fig. 29. Aldebaran, the "leader" (of the Pleiades), was also 

known to the Arabs as "The Eye of the Bull," "The 

Heart of the Bull," and "The Great Camel" 

(Hubble). 

Like Betelgeuse and Antares, it is notable for its red color, which accounts for 
the fact that its image on this photograph is hardly more conspicuous than 
the images of stars which are actually much fainter but contain a larger pro- 
portion of blue light, to which the photographic plates here employed are 
more sensitive than to red or yellow. Aldebaran is about 50 light-years 
from the earth. Interferometer measures, now in progress on Mount 
Wilson, indicate that its angular diameter is about 0.020 of a second. 



THE NEW HEAVENS 

dimensions. The mode of formation of systems 
like our own, and of other systems numerously illus- 
trated in the heavens, is one of the most fascinating 
problems of astronomy. Much light has been 
thrown on it by recent investigations, rendered pos- 
sible by the development of new and powerful in- 
struments and by advances in physics of the most 
fundamental character. All the evidence confirms 
the existence of dwarf and giant stars, but much 
work must be done before the entire course of 
stellar evolution can be explained. 



[ 60 ] 



CHAPTER III 
COSMIC CRUCIBLES 

"Shelter during Raids," marking the entrance 
to underground passages, was a sign of common oc- 
currence and sinister suggestion throughout London 
during the war. With characteristic ingenuity and 
craftiness, ostensibly for purposes of peace but with 
bomb-carrying capacity as a prime specification, the 
Zeppelin had been developed by the Germans to a 
point where it seriously threatened both London and 
Paris. Searchlights, range-finders, and anti-aircraft 
guns, surpassed by the daring ventures of British 
and French airmen, would have served but little 
against the night invader except for its one fatal de- 
fect — the inflammable nature of the hydrogen gas 
that kept it aloft. A single explosive bullet served 
to transform a Zeppelin into a heap of scorched 
and twisted metal. This characteristic of hydrogen 
caused the failure of the Zeppelin raids. 

Had the war lasted a few months longer, however, 
the work of American scientists would have made 
our counter-attack in the air a formidable one. At 
the signing of the armistice hundreds of cylinders of 
compressed helium lay at the docks ready for ship- 
ment abroad. Extracted from the natural gas of 
Texas wells by new and ingenious processes, this 

[61 ] 



THE NEW HEAVENS 

substitute for hydrogen, almost as light and abso- 
lutely uninflammable, produced in quantities of mil- 
lions of cubic feet, would have made the dirigibles 
of the Allies masters of the air. The special proper- 
ties of this remarkable gas, previously obtainable 
only in minute quantities, would have sufficed to re- 
verse the situation. 

SOLAR HELIUM 

Helium, as its name implies, is of solar origin. In 
1868, when Lockyer first directed his spectroscope 
to the great flames or prominences that rise thou- 
sands of miles, sometimes hundreds of thousands, 
above the surface of the sun, he instantly identified 
the characteristic red and blue radiations of hydro- 
gen. In the yellow, close to the position of the well- 
known double line of sodium, but not quite coinci- 
dent with it, he detected a new line, of great bril- 
liancy, extending to the highest levels. Its similar- 
ity in this respect with the lines of hydrogen led him 
to recognize the existence of a new and very light 
gas, unknown to terrestrial chemistry. 

Many years passed before any chemical labora- 
tory on earth was able to match this product of the 
great laboratory of the sun. In 1896 Ramsay at 
last succeeded in separating helium, recognized by 
the same yellow line in its spectrum, in minute 
quantities from the mineral uraninite. Once avail- 
able for study under electrical excitation in vacuum 
tubes, helium was found to have many other lines 
in its spectrum, which have been identified in the 

1 62 ] 



COSMIC CRUCIBLES 

spectra of solar prominences, gaseous nebulae, and 
hot stars. Indeed, there is a stellar class known as 




Fig. 30. Solar prominences, photographed with the spectro- 
heliograph without an eclipse (Ellerman). 

In these luminous gaseous clouds, which sometimes rise to elevations exceeding 
half the sun's diameter, the new gas helium was discovered by Lockyer in 
1868. Helium was not found on the earth until 1896. Since then it has 
been shown to be a prominent constituent of nebulae and hot stars. 



helium stars, because of the dominance of this gas 
in their atmospheres. 

The chief importance of helium lies in the clue it 
has afforded to the constitution of matter and the 
transmutation of the elements. Radium and other 

[ 63 ] 



THE NEW HEAVENS 

radioactive substances, such as uranium, spontane- 
ously emit negatively charged particles of extremely 
small mass (electrons), and also positively charged 
particles of much greater mass, known as alpha par- 
ticles. Rutherford and Geiger actually succeeded in 
counting the number of alpha particles emitted per 
second by a known mass of radium, and showed 
that these were charged helium atoms. 

To discuss more at length the extraordinary char- 
acteristics of helium, which plays so large a part in 
celestial affairs, would take us too far afield. Let 
us therefore pass to another case in which a funda- 
mental discovery, this time in physics, was first 
foreshadowed by astronomical observation. 

SUN-SPOTS AS MAGNETS 

No archaeologist, whether Young or Champollion 
deciphering the Rosetta Stone, or Rawlinson copy- 
ing the cuneiform inscription on the cliff of Behis- 
tun, was ever faced by a more fascinating problem 
than that which confronts the solar physicist en- 
gaged in the interpretation of the hieroglyphic lines 
of sun-spot spectra. The colossal whirling storms 
that constitute sun-spots, so vast that the earth 
would make but a moment's scant mouthful for 
them, differ materially from the general light of the 
sun when examined WTth the spectroscope. Observ- 
ing them visually many years ago, the late Professor 
Young, of Princeton, found among their complex 
features a number of double lines which he naturally 
attributed, in harmony with the physical knowledge 

[6 4 ] 



COSMIC CRUCIBLES 

of the time, to the effect of "reversal" by super- 
posed layers of vapors of different density and tern- 




Fig. 31. The 150-foot tower telescope of the Mount 
Wilson Observatory. 

An image of the sun about 16 inches indiameter is formed in the laboratory at 
the base of the tower. Below this, in a well extending 80 feet into the earth, 
is the powerful spectroscope with which the magnetic fields in sun-spots 
and the general magnetic field of the sun are studied. 

perature. What he actually saw, however, as was 
proved at the Mount Wilson Observatory in ic 

[6 5 ] 



THE NEW HEAVENS 

was the effect of a powerful magnetic field on radia- 
tion, now known as the Zeeman effect. 

Faraday was the first to detect the influence of 
magnetism on light. Between the poles of a large 
electromagnet, powerful for those days (1845), he 
placed a block of very dense glass. The plane of 
polarization of a beam of light, which passed un- 
affected through the glass before the switch was 
closed, was seen to rotate when the magnetic field 
was produced by the flow of the current. A similar 
rotation is now familiar in the well-known tests of 
sugars — laevulose and dextrose — which rotate plane- 
polarized light to left and right, respectively. 

But in this first discovery of a relationship be- 
tween light and magnetism Faraday had not taken 
the more important step that he coveted — to deter- 
mine whether the vibration period of a light-emit- 
ting particle is subject to change in a magnetic field. 
He attempted this in 1862 — the last experiment of 
his life. A sodium flame was placed between the 
poles of a magnet, and the yellow lines were watched 
in a spectroscope when the magnet was excited. 
No change could be detected, and none was found 
by subsequent investigators until Zeeman, of Leiden, 
with more powerful instruments made his famous 
discovery, the twenty-fifth anniversary of which 
has recently been celebrated. 

His method of procedure was similar to Faraday's, 
but his magnet and spectroscope were much more 
powerful, and a theory due to Lorentz, predicting 
the nature of the change to be expected, was avail- 

[ 66] 



COSMIC CRUCIBLES 

able as a check on his results. When the current 
was applied the lines were seen to widen. In a still 
more powerful magnetic field each of them split into 
two components (when the observation was made 




Fig. 32. Pasadena Laboratory of the Mount Wilson 
Observatory. 

Showing the large magnet (on the left) and the spectroscopes used for the study 
of the effect of magnetism on radiation. A single line in the spectrum is 
split by the magnetic field into from three to twenty-one components, as 
illustrated in Fig. 34. The corresponding lines in the spectra of sun-spots 
are split up in precisely the same way, thus indicating the presence of power- 
ful magnetic fields in the sun. 



along the lines of force), and the light of the compo- 
nents of each line was found to be circularly polar- 
ized in opposite directions. Strictly in harmony 
with Lorentz's theory, this splitting and polariza- 
tion proved the presence in the luminous vapor of 

[ 6 7 ] 



THE NEW HEAVENS 

exactly such negatively charged electrons as had 
been indicated there previously by very different 
experimental methods. 

In 1908 great cyclonic storms, or vortices, were 
discovered at the Mount Wilson Observatory cen- 
tring in sun-spots. Such whirling masses of hot 
vapors, inferred from Sir Joseph Thomson's results 
to contain electrically charged particles, should give 
rise to a magnetic field. This hypothesis at once 
suggested that the double lines observed by Young 
might really represent the Zeeman effect. The test 
was made, and all the characteristic phenomena of 
radiation in a magnetic field were found. 

Thus a great physical experiment is constantly 
being performed for us in the sun. Every large sun- 
spot contains a magnetic field covering many thou- 
sands of square miles, within which the spectrum 
lines of iron, manganese, chromium, titanium, vana- 
dium, calcium, and other metallic vapors are so 
powerfully affected that their widening and split- 
ting can be seen with telescopes and spectroscopes 
of moderate size. 

THE TOWER TELESCOPE 

Both of these illustrations show how the physicist 
and chemist, when adequately armed for astronom- 
ical attack, can take advantage in their studies of 
the stupendous processes visible in cosmic crucibles, 
heated to high temperatures and influenced, as in 
the case of sun-spots, by intense magnetic fields. 
Certain modern instruments, like the 60-foot and 

[ 68 ] 



COSMIC CRUCIBLES 

150-foot tower telescopes on Mount Wilson, are 
especially designed for observing the course of these 
experiments. The second of these telescopes pro- 
duces at a fixed point in a laboratory an image of 












Fig. 33. Sun-spot vortex in the upper hydrogen atmosphere. 
(Benioff). 

Photographed with the spectroheliograph. The electric vortex that causes the 
magnetic field of the spot lies at a lower level, and is not shown by such 
photographs. 

the sun about 16 inches in diameter, thus enlarging 
the sun-spots to such a scale that the magnetic 
phenomena of their various parts can be separately 
studied. This analysis is accomplished with a spec- 
troscope 80 feet in length, mounted in a subter- 
ranean chamber beneath the tower. The varied re- 
sults of such investigations cannot be described here. 
Only one of them may be mentioned — the discovery 

[69] 



THE NEW HEAVENS 

that the entire sun, rotating on its axis, is a great 
magnet. Hence we may reasonably infer that every 
star, and probably every planet, is also a magnet, 
as the earth has been known to be since the days of 
Gilbert's "De Magnete." Here lies one of the best 
clues for the physicist who seeks the cause of mag- 
netism, and attempts to produce it, as Barnett has 
recently succeeded in doing, by rapidly whirling 
masses of metal in the laboratory. 

Perhaps a word of caution should be interpolated 
at this point. Solar magnetism in no wise accounts 
for the sun's gravitational power. Indeed, its at- 
traction cannot be felt by the most delicate instru- 
ments at the distance of the earth, and would still 
be unknown were it not for the influence of magne- 
tism on light. 

Auroras, magnetic storms, and such electric cur- 
rents as those that recently deranged several Atlan- 
tic cables are due, not to the magnetism of the sun 
or its spots, but probably to streams of electrons, 
shot out from highly disturbed areas of the solar 
surface surrounding great sun-spots, traversing 
ninety-three million miles of the ether of space, 
and penetrating deep into the earth's atmosphere. 
These striking phenomena lead us into another 
chapter of physics, which limitations of space for- 
bid us to pursue. 

STELLAR CHEMISTRY 

Let us turn again to chemistry, and see where 
experiments performed in cosmic laboratories can 

[70] 



COSMIC CRUCIBLES 

serve as a guide to the investigator. A spinning 
solar tornado, incomparably greater in scale than 
the devastating whirlwinds that so often cut narrow 




Fig. 34. Splitting of spectrum lines by a magnetic field 

(Babcock). 

The upper and lower strips show lines in the spectrum of chromium, observed 
without a magnetic field. When subjected to the influence of magnetism, 
these single lines are split into several components. Thus the first line on 
the right is resolved by the field into three components, one of which (plane 
polarized) appears in the second strip, while the other two, which are po- 
larized in a plane at right angles to that of the middle component, are shown 
on the third strip. The next line is split by the magnetic field into twelve 
components, four of which appear in the second strip and eight in the third. 
The magnetic fields in sun-spots affect these lines in precisely the same way. 



paths of destruction through town and country in 
the Middle West, gradually gives rise to a sun-spot. 
The expansion produced by the centrifugal force at 
the centre of the storm cools the intensely hot gases 

[71 ] 



THE NEW HEAVENS 

of the solar atmosphere to a point where chemical 
union can occur. Titanium and oxygen, too hot to 
combine in most regions of the sun, join to form the 
vapor of titanium oxide, characterized in the sun- 
spot spectrum by fluted bands, made up of hundreds 
of regularly spaced lines. Similarly magnesium and 
hydrogen combine as magnesium hydride and cal- 
cium and hydrogen form calcium hydride. None of 
these compounds, stable at the high temperatures of 
sun-spots, has been much studied in the laboratory. 
The regions in which they exist, though cooler than 
the general atmosphere of the sun, are at tempera- 
tures of several thousand degrees, attained in our 
laboratories only with the aid of such devices as 
powerful electric furnaces. 

It is interesting to follow our line of reasoning to 
the stars, which differ widely in temperature at 
various stages in their life-cycle.* A sun-spot is a 
solar tornado, wherein the intensely hot solar vapors 
are cooled by expansion, giving rise to the com- 
pounds already named. A red star, in Russell's 
scheme of stellar evolution, is a cooler sun, vast in 
volume and far more tenuous than atmospheric air 
when in the initial period of the "giant" stage, but 
compressed and denser than water in the "dwarf" 
stage, into which our sun has already entered as it 
gradually approaches the last phases of its existence. 
Therefore we should find, throughout the entire 
atmosphere of such stars, some of the same com- 
pounds that are produced within the comparatively 
* See Chapter II. 

[72] 



COSMIC CRUCIBLES 

small limits of a sun-spot. This, of course, on the 
correct assumption that sun and stars are made of 
the same substances. Fowler has already identified 
the bands of titanium oxide in such red stars as the 
giant Betelgeuse, and in others of its class. It is 




Fig. 35. Electric furnace in the Pasadena laboratory of the 
Mount Wilson Observatory. 

With which the chemical phenomena observed in sun-spots and red 
stars are experimentally imitated. 



safe to predict that an interesting chapter in the 
chemistry of the future will be based upon the study 
of such compounds, both in the laboratory and under 
the progressive temperature conditions afforded by 
the countless stellar "giants" and "dwarfs" that 
precede and follow the solar state. 

[73 ] 



THE NEW HEAVENS 

ASTROPHYSICAL LABORATORIES 

It is precisely in this long sequence of physical 
and chemical changes that the astrophysicist and 
the astrochemist can find the means of pushing home 
their attack. It is true, of course, that the labora- 
tory investigator has a great advantage in his ability 
to control his experiments, and to vary their progress 
at will. But by judicious use of the transcendental 
temperatures, far outranging those of his furnaces, 
and extreme conditions, which he can only partially 
imitate, afforded by the sun, stars, and nebulae, he 
may greatly widen the range of his inquiries. The 
sequence of phenomena seen during the growth of 
a sun-spot, or the observation of spots of different 
sizes, and the long series of successive steps that 
mark the rise and decay of stellar life, resemble 
the changes that the experimenter brings about as 
he increases and diminishes the current in the coils 
of his magnet or raises and lowers the temperature 
of his electric furnace, examining from time to time 
the spectrum of the glowing vapors, and noting the 
changes shown by the varying appearance of their 
lines. 

Astronomical observations of this character, it 
should be noted, are most effective when constantly 
tested and interpreted by laboratory experiment. 
Indeed, a modern astrophysical observatory should 
be equipped like a great physical laboratory, pro- 
vided on the one hand with telescopes and accessory 
apparatus of the greatest attainable power, and on 

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THE NEW HEAVENS 

the other with every device known to the investi- 
gator of radiation and the related physical and 
chemical phenomena. Its telescopes, especially de- 
signed with the aims of the physicist and chemist 
in view, bring images of sun, stars, nebulae, and other 
heavenly bodies within the reach of powerful spec- 
troscopes, sensitive bolometers and thermopiles, and 
the long array of other appliances available for the 
measurement and analysis of radiation. Its elec- 
tric furnaces, arcs, sparks, and vacuum tubes, its 
apparatus for increasing and decreasing pressure, 
varying chemical conditions, and subjecting lumi- 
nous gases and vapors to the influence of electric 
and magnetic fields, provide the means of imitating 
celestial phenomena, and of repeating and interpret- 
ing the experiments observed at the telescope. And 
the advantage thus derived, as we have seen, is 
not confined to the astronomer, who has often been 
able, by making fundamental physical and chemical 
discoveries, to repay his debt to the physicist and 
chemist for the apparatus and methods which he 
owes to them. 

NEWTON AND EINSTEIN 

Take, for another example, the greatest law of 
physics — Newton's law of gravitation. Huge balls 
of lead, as used by Cavendish, produce by their 
gravitational effect a minute rotation of a delicately 
suspended bar, carrying smaller balls at its extremi- 
ties. But no such feeble means sufficed for New- 
ton's purpose. To prove the law of gravitation he 

[76] 



COSMIC CRUCIBLES 

had recourse to the tremendous pull on the moon of 
the entire mass of the earth, and then extended his 
researches to the mutual attractions of all the bodies 
of the solar system. Later Herschel applied this 




Fig. 38. The Cavendish experiment. 

Two lead balls, each two inches in diameter, are attached to the ends of a torsion 
rod six feet long, which is suspended by a fine wire. The experiment consists 
in measuring the rotation of the suspended system, caused by the gravita- 
tional attraction of two lead spheres, each twelve inches in diameter, acting 
on the two small lead balls. 



law to the suns which constitute double stars, and 
to-day Adams observes from Mount Wilson stars 
falling with great velocity toward the centre of the 
galactic system under the combined pull of the mil- 
lions of objects that compose it. Thus full advan- 
tage has been taken of the possibility of utilizing 
the great masses of the heavenly bodies for the dis- 

[77] 



THE NEW HEAVENS 

covery and application of a law of physics and its 
reciprocal use in explaining celestial motions. 

Or consider the Einstein theory of relativity, the 
truth or falsity of which is no less fundamental to 
physics. Its inception sprang from the Michelson- 
Morley experiment, made in a laboratory in Cleve- 
land, which showed that motion of the earth through 
the ether of space could not be detected. All of the 
three chief tests of Einstein's general theory are 
astronomical — because of the great masses required 
to produce the minute effects predicted: the motion 
of the perihelion of Mercury, the deflection of the 
light of a star by the attraction of the sun, and the 
shift of the lines of the solar spectrum toward the 
red — questions not yet completely answered. 

But it is in the study of the constitution of matter 
and the evolution of the elements, the deepest and 
most critical problem of physics and chemistry, 
that the extremes of pressure and temperature in 
the heavenly bodies, and the prevalence of other 
physical conditions not yet successfully imitated on 
earth, promise the greatest progress. It fortunately 
happens that astrophysical research is now at the 
very apex of its development, founded as it is upon 
many centuries of astronomical investigation, rejuve- 
nated by the introduction into the observatory of all 
the modern devices of the physicist, and strength- 
ened with instruments of truly extraordinary range 
and power. These instruments bring within reach 
experiments that are in progress on some minute 

[78 ] 



COSMIC CRUCIBLES 

region of the sun's disk, or in some star too distant 
even to be glimpsed with ordinary telescopes. In- 
deed, the huge astronomical lenses and mirrors now 
available serve for these remote light-sources exactly 
the purpose of the lens or mirror employed by the 
physicist to project upon the slit of his spectroscope 
the image of a spark or arc or vacuum tube within 
which atoms and molecules are exposed to the 
influence of the electric discharge. The physicist 
has the advantage of complete control over the ex- 
perimental conditions, while the astrophysicist must 
observe and interpret the experiments performed for 
him in remote laboratories. In actual practice, the 
two classes of work must be done in the closest con- 
junction, if adequate utilization is to be made of 
either. And this is only natural, for the trend of 
recent research has made clear the fact that one of 
the three greatest problems of modern astronomy 
and astrophysics, ranking with the structure of the 
universe and the evolution of celestial bodies, is 
the constitution of matter. Let us see why this is so. 

TRANSMUTATION OF THE ELEMENTS 

The dream of the alchemist was to transmute one 
element into another, with the prime object of pro- 
ducing gold. Such transmutation has been actually 
accomplished within the last few years, but the 
process is invariably one of disintegration — the more 
complex elements being broken up into simpler con- 
stituents. Much remains to be done in this same 
direction; and here the stars and nebulae, which 

[79] 



THE NEW HEAVENS 

show the spectra of the elements under a great 
variety of conditions, should help to point the way. 
The progressive changes in spectra, from the ex- 
clusive indications of the simple elements hydrogen, 
helium, nitrogen, possibly carbon, and the terrestri- 
ally unknown gas nebulium in the gaseous nebulae, 
to the long list of familiar substances, including 
several chemical compounds, in the red stars, may 
prove to be fundamentally significant when ade- 
quately studied from the standpoint of the investi- 
gator of atomic structure. The existing evidence 
seems to favor the view, recently expressed by Saha, 
that many of these differences are due to varying 
degrees of ionization, the outer electrons of the atoms 
being split off by high temperature or electrical 
excitation. It is even possible that cosmic cruci- 
bles, unrivalled by terrestrial ones, may help ma- 
terially to reveal the secret of the formation of 
complex elements from simpler ones. Physicists 
now believe that all of the elements are compounded 
of hydrogen atoms, bound together by negative elec- 
trons. Thus helium is made up of four hydrogen 
atoms, yet the atomic weight of helium (4) is less 
than four times that of hydrogen (1.008). The 
difference may represent the mass of the electrical 
energy released when the transmutation occurred. 
Eddington has speculated in a most interesting 
way on this possible source of stellar heat in his 
recent presidential address before the British Asso- 
ciation for the Advancement of Science (see Nature, 
September 2, 1920). He points out that the old 

[80] 




Fig. 39. The Trifid Nebula in Sagittarius (Ritchey). 

The gas "nebulium," not yet found on the earth, is the most characteristic con- 
stituent of irregular nebulae. Nebulium is recognized by two green lines 
in its spectrum, which cause the green color of nebulas of the gaseous type. 



THE NEW HEAVENS 

contraction hypothesis, according to which the 
source of solar and stellar heat was supposed to re- 
side in the slow condensation of a radiating mass of 
gas under the action of gravity, is wholly inadequate 
to explain the observed phenomena. If the old 
view were correct, the earlier history of a star, from 
the giant stage of a cool and diaphanous gas to 
the period of highest temperature, would be run 
through within eighty thousand years, whereas we 
have the best of evidence that many thousands of 
centuries would not suffice. Some other source of 
energy is imperatively needed. If 5 per cent of a 
star's mass consists originally of hydrogen atoms, 
which gradually combine in the slow process of 
time to form more complex elements, the total heat 
thus liberated would more than suffice to account 
for all demands, and it would be unnecessary to 
assume the existence of any other source of heat. 

COSMIC PRESSURES 

This, it may fairly be said, is very speculative, 
but the fact remains that celestial bodies appear to 
be the only places in which the complex elements 
may be in actual process of formation from their 
known source — hydrogen. At least we may see 
what a vast variety of physical conditions these 
cosmic crucibles afford. At one end of the scale we 
have the excessively tenuous nebulae, the luminosity 
of which, mysterious in its origin, resembles the 
electric glow in our vacuum tubes. Here we can 
detect only the lightest and simplest of the ele- 

[ 82 ] 




Fig. 40. Spiral nebula in Ursa Major (Ritchey). 

Luminous matter, in every variety of physical and chemical state, is available 
for study in the most diverse celestial objects, from the spiral and irregular 
nebula; through all the types of stars. Doctor van Maanen's measures of 
the Mount Wilson photographs indicate outward motion along the arms of 
spiral nebulae, while the spectroscope shows them to be whirling at enor- 
mous velocities. 



THE NEW HEAVENS 

ments. In the giant stars, also extremely tenuous 
(the density of Betelgeuse can hardly exceed one- 
thousandth of an atmosphere) we observe the spec- 
tra of iron, manganese, titanium, calcium, chromium, 
magnesium, vanadium, and sodium, in addition to 
titanium oxide. The outer part of these bodies, 
from which light reaches us, must therefore be at a 
temperature of only a few thousand degrees, but 
vastly higher temperatures must prevail at their 
centres. In passing up the temperature curve more 
and more elements appear, the surface temperature 
rises, and the internal temperature may reach mil- 
lions of degrees. At the same time the pressure 
within must also rise, reaching enormous figures in 
the last stages of stellar life. Cook has calculated 
that the pressure at the centre of the earth is be- 
tween 4,000 and 10,000 tons per square inch, and 
this must be only a very small fraction of that at- 
tained within larger celestial bodies. Jeans has 
computed the pressure at the centre of two colliding 
stars as they strike and flatten, and finds it may be 
of the order of 1,000,000,000 tons per square inch — 
sufficient, if their diameter be equal to that of the 
sun — to vaporize them 100,000 times over. 

Compare these pressures with the highest that 
can be produced on earth. If the German gun that 
bombarded Paris were loaded with a solid steel pro- 
jectile of suitable dimensions, a muzzle velocity of 
6,000 feet per second could be reached. Suppose 
this to be fired into a tapered hole in a great block of 
steel. The instantaneous pressure, according to 

[ 84] 



COSMIC CRUCIBLES 

Cook, would be about 7,000 tons per square inch, 
only i5 Voo' °f tnat possible through the collision of 
the largest stars. 

Finally, we may compare the effects of light pres- 




Fig. 41. Mount San Antonio as seen from Mount Wilson. 

Michelson is measuring the velocity of light between stations on Mount Wilson 
and Mount San Antonio. Astronomical observations afford the best'means, 
however, of detecting any possible difference between the velocities of light 
of different colors. From studies of variable stars in the cluster Messier 5 
Shapley concludes that if there is any difference between the velocities of 
blue and yellow light in free space it cannot exceed two inches in one second, 
the time in which light travels 186,000 miles. 



sure on the earth and stars. Twenty years ago 
Nichols and Hull succeeded, with the aid of the 
most sensitive apparatus, in measuring the minute 
displacements produced by the pressure of light. 
The effect is so slight, even with the brightest light- 

[ 85 ] 



THE NEW HEAVENS 

sources available, that great experimental skill is 
required to measure it. Yet in the case of some of 
the larger stars Eddington calculates that one-half 
of their mass is supported by radiation pressure, 
and this against their enormous gravitational at- 
traction. In fact, if their mass were as great as ten 
times that of the sun, the radiation pressure would 
so nearly overcome the pull of gravitation that they 
would be likely to break up. 

But enough has been said to illustrate the wide 
variety of experimental devices that stand at our 
service in the laboratories of the heavens. Here the 
physicist and chemist of the future will more and 
more frequently supplement their terrestrial ap- 
paratus, and find new clues to the complex problems 
which the amazing progress of recent years has al- 
ready done so much to solve. 

PRACTICAL VALUE OF RESEARCHES ON THE CONSTI- 
TUTION OF MATTER 

The layman has no difficulty in recognizing the 
practical value of researches directed toward the 
improvement of the incandescent lamp or the in- 
creased efficiency of the telephone. He can see the 
results in the greatly decreased cost of electric 
illumination and the rapid extension of the range of 
the human voice. But the very men who have 
made these advances, those who have succeeded be- 
yond all expectation in accomplishing the economic 
purposes in view, are most emphatic in their insis- 

[ 86 1 



COSMIC CRUCIBLES 

tence upon the importance of research of a more 
fundamental character. Thus Vice-President J. J. 
Carty, of the American Telephone and Telegraph 
Company, who directs its great Department of 
Development and Research, and Doctor W. J. 
Whitney, Director of the Research Laboratory of 
the General Electric Company, have repeatedly 
expressed their indebtedness to the investigations of 
the physicist, made with no thought of immediate 
practical return. Faraday, studying the laws of 
electricity, discovered the principle which rendered 
the dynamo possible. Maxwell, Henry, and Hertz, 
equally unconcerned with material advantage, made 
wireless telegraphy practicable. In fact, all truly 
great advances are thus derived from fundamental 
science, and the future progress of the world will 
be largely dependent upon the provision made for 
scientific research, especially in the fields of physics 
and chemistry, which underlie all branches of engi- 
neering. 

The constitution of matter, therefore, instead of 
appealing as a subject to research only to the natural 
philosopher or to the general student of science, is 
a question of the greatest practical concern. Al- 
ready the by-products of investigations directed 
toward its elucidation have been numerous and 
useful in the highest degree. Helium has been 
already cited; X-rays hardly require mention; ra- 
dium, which has so materially aided sufferers from 
cancer, is still better known. Wireless telephony 
and transcontinental telephony with wires were both 

[8 7 ] 



THE NEW HEAVENS 

rendered possible by studies of the nature of the 
electric discharge in vacuum tubes. Thus the 
"practical man," with his distrust of "pure" sci- 
ence, need not resent investments made for the pur- 
pose of advancing our knowledge of such fundamen- 
tal subjects as physics and chemistry. On the con- 
trary, if true to his name, he should help to multiply 
them many fold in the interest of economic and 
commercial development. 



[88] 



